Semiconductor dies include collections of transistors and other components. Commonly, these substrates are semiconductor materials, and, in particular, silicon. Additionally, these substrates are conventionally thicker than necessary to obtain desirable device behavior. The semiconductor dies are singulated or diced from a semiconductor wafer.
Thick dies have advantages during semiconductor assembly. During assembly of semiconductor dies such as packaging, a semiconductor die endures dozens of processes, high temperatures, and transfers between tools or even fabrication sites. During these transfers the semiconductor die can break, resulting in a loss of time and resources. Thick dies are less likely to be damaged during manufacturing.
Despite the advantages of thick dies listed above, thin dies may be preferred for some assembly processes. One example of assembly of thin semiconductor dies is construction of stacked ICs. Stacked ICs increase device functionality and decrease die size by stacking dies vertically. Similar to high-rise towers that fit more office space in a smaller land area, stacked ICs offer more space for transistors and other components while occupying the same area.
In stacked ICs, a second die is stacked on a first die allowing construction to expand into three dimensions (3D). Stacked ICs allow products with a greater number of components to fit in small form factors. Component density of a semiconductor die is number of components in the die divided by the die area. Thus, stacking a die on an identical die results in approximately double component density. When a second die is stacked on a first die, the two dies share the same packaging and communicate to external devices through the packaging.
Conventionally, the second die is coupled to packaging and external devices with through silicon vias located in the first die. Through silicon vias are limited in aspect ratio based, in part, on the manufacturing technique selected. As a result, the height of the first die is limited in order to ensure the through silicon via may extend the entire height of the first die. The through silicon via should extend the entire height to create a conducting path from a packaging substrate to the second die. As the height of the first die decreases to accommodate the through silicon via manufacturing, the first die loses structural strength.
During assembly of the first die on a packaging substrate, the thin die may bend. The bending results from insufficient mechanical strength of the thin die to withstand heat cycles and thermal mechanical changes during the assembly process. Bending of the thin die may result in broken or undesirable function of components in the thin die. Additionally, physical bending may result in an undesirable semiconductor die geometry or size.
Thus, there is a need for reducing bending in a semiconductor die during semiconductor assembly.